IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

308 IBM TotalStorage DS6000 Series: Performance Monitoring and Tuning

The underlying effect of application performance boost control significantly differs between

various versions of Windows. In Windows 2000, the application boost GUI settings have the

following counterpart in the Registry:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\PriorityControl\

Win32PrioritySeparation

The Win32PrioritySeparation Registry values in Windows 2000 Server are:

򐂰 38 for applications performance of Programs

򐂰 24 for background services of Background services

It is a good tuning practice to disable any prioritization of foreground applications if services

serving users are running in the background. You should set this window according to your

needs. By clicking the Programs setting, the process priority is given to the foreground

applications, and by clicking the Background services setting, the priority is given to

background processes.

We strongly recommend that you use only the GUI interface for these settings in order to

always get valid, appropriate, operating system revision-specific, and optimal values in the

registry.

9.2.2 Virtual memory

Memory paging occurs when memory resources required by the server exceed the physical

amount of memory installed in the server. Memory can be accessed at over 1 GB/s, whereas

a single disk drive provides data at about 2–3 MB/s. Servers accessing information from disk

run much slower than when the information can be accessed directly from memory.

Windows Server 2003 and 2000, as most other server operating systems, employ

virtual

memory

techniques that allow applications to address greater amounts of memory than what

is physically available. Memory pressure occurs when the demand for physical memory

exceeds the amount of installed memory, causing the operating system to

page excess

memory onto a disk drive.

Paging is the process whereby blocks of data are swapped from the physical memory to a file

on the hard disk. The

paging file is page file.SYS. The combination of the paging file and the

physical memory is known as

virtual memory. Some paging is normal for the usual operating

system, but when excessive consistent paging which is called

thrashing occurs, it affects the

system performance. To avoid this, paging should be minimized.

You can control the size of the paging file and this can improve performance if you specify the

minimum value to be what the server normally allocates during the peak time of the day. This

ensures that no processing resources are lost to the allocation and segmentation of the

paging space.

To configure the page file size:

1. Open the Control Panel.

2. Open System.

3. Select Advanced.

4. Click Performance Option.

5. Click Change and the window shown in Figure 9-2 on page 309 will appear.

6. Enter new values for Initial Size (MB) and Maximum Size (MB) and click OK.

Chapter 9. Open system servers - Windows 309

Window Server 2003 has several options for configuring the page file that previous versions

of Windows did not. Windows Server 2003 has introduced new settings for virtual memory

configuration, including letting the system manage the size of the page file, or to have no

page file at all. If you let Windows manage the size, it will create a page file of a size equal to

physical memory plus 1MB. This is the minimum amount of space required to create a

memory dump in the event the server encounters a STOP event (blue screen).

Figure 9-2 Virtual memory settings

You can set the initial size and the maximum size of the paging file for every drive. The

maximum number of page files is 16 and the maximum size is 4 GB per page file. This means

a maximum of total page size is 64 GB. Total size of page file is used as one page file by the

operating system. For a file server, set the minimum to the recommended value, as shown in

the window. For other server applications the recommendation varies. For a discussion of

recommended values refer to the publication Tuning IBM eServer xSeries Servers for

Performance, SG24-5287.

The size of the registry does not affect performance.

In a production environment with well-written server applications, hard page faults should not

constantly occur. If there is any sustained paging, check the available bytes in the Task

Manager.

򐂰 If Available Bytes is less than 20 percent of installed RAM, then add more RAM.

򐂰 If Available Bytes is much greater than 20 percent of total installed RAM, then the

application cannot make use of additional RAM, so the only solution is to optimize the

page device.

Create separate

page file for each

disk to improve

system performance